Safety Insight: Testing and Characterization of Lithium-Ion Batteries
The battery has come a long way since the introduction of the “voltaic pile” by Alessandro Volta in the year 1800. Today, there are many different types of batteries used in many different applications. One type of battery that has become common because of its versatility and high energy density is the lithium-ion battery, which was first introduced in the 1970’s.
There are many variations of today’s lithium-ion batteries. Some of the most commonly found are lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide (NMC), lithium-ion phosphate, and lithium titanate. Six different parameters arranged in a “spider web” (see figure below) can help determine which battery is best for a particular application. Specific energy (energy density), cost, specific power, life span, performance, and safety differ between each variety of lithium-ion battery.
The most common lithium-ion battery for the everyday consumer is lithium cobalt oxide (LiCoO2). These can be found in items such as cell phones and laptops. The benefit of lithium cobalt oxide is its high specific energy, as seen in the diagram above. The drawbacks are a low overall life span, low specific power (load capability), and lithium cobalt oxide may be considered a less-safe lithium-ion battery type because of its low thermal stability. However, lithium-ion batteries are generally considered safe for use in consumer products.
There are many tests used in battery diagnostics. Because of the complex structure and use of lithium-ion batteries, no single test will accurately characterize the battery’s health. Many tests are conducted to determine or estimate the current state of the battery and time until the battery’s end of life. The parameters that are measured in testing may include voltage and internal resistance, but additional tests may be conducted that include coulomb counting or electrochemical impedance spectroscopy (EIS). These tests may only provide estimations of the overall battery life. If possible, testing on batteries that are operating as part of their intended systems may help to provide more accurate results.
The chemical makeup of the battery, including the composition of the electrolyte and cathode, play a large role in overall battery health. In general battery testing to determine the state of the battery or estimate battery life, certain interactions between these chemicals may not be captured or certain conditions, such as environmental temperature, may not be considered.
Lithium-Ion Battery Safety
Lithium-ion batteries occasionally become news-worthy after a fire or explosion of a damaged cell but considering the staggering (and growing) number of lithium-ion batteries in the hands and pockets of consumers every day, they can be considered relatively safe. There are several ways that lithium ion batteries can fail, and in the event of failure, there is a good chance of fire, explosion, or release of corrosive chemicals.
One way that lithium-ion batteries can fail is through a failure in the porous separator. If this separator becomes compromised, the flow of lithium ions may become uncontrolled, resulting in a thermal runaway which may lead to a fire. Another way that a battery can fail is through improper environmental use. A battery can become compromised if it is used in an environment that is above or below its temperature limits, typically 5-45oC. Finally, defects in the batteries that are not discovered through testing can cause battery failure. This could be a range of issues such as uneven separators or dry areas within the battery, which will contribute to localized areas of poor conductivity.
Despite the relative safety of lithium-ion batteries, there is still significant research being done to reduce the risk of failure, along with new types of lithium-ion batteries in development. To ensure the lowest risk, it’s important to always use batteries that are certified for use in their intended application.
How can DEKRA Process Safety Help You?
DEKRA Process Safety has the facilities and the equipment required to conduct battery testing to determine the safety and performance characteristics of your battery and battery packs. With knowledgeable laboratory staff in the Americas, Europe and Asia, we take a customized approach to meet your testing objectives. The full range of battery tests is carried out at our IECEE CB-approved laboratory and we can test to IEC, EN and UN standards. Our experienced staff and state-of-the-art battery testing laboratory can help you determine which tests are needed for your product to meet national and international requirements. With years of testing experience and certification services, we are well placed to assist you with your compliance, testing and analysis needs.
In addition to testing, we also offer a comprehensive range of battery hazards analysis and quality assurance solutions that include certification, consultancy, and training so that you can develop better, safer and more competitive products.